Self-organized deposition morphologies of polymethyl methacrylate nanoparticles in droplets during drying process

The evaporation process of droplets containing nano-scale solid particles has attracted widespread attention recently. However, the laws and mechanisms underlying the formation of deposition morphologies during the evaporation process are still unclear. Herein, we prepare a mixed solution of water and ethanol containing polymethyl methacrylate nanoparticles, and research the formed morphologies of PMMA nanoparticles by self-organizing during droplet evaporation. By controlling the solvent composition and PMMA concentration of the mixture, a variety of deposition morphologies, such as stripe, brick block, arch, island and irregularity were obtained, and their formation mechanism is explained from the perspective of convection and surface tension. It is found that convection and PMMA concentration affect the regularity, continuity, crack depth and crack width of the deposition morphologies, and the corresponding deposition morphology can be obtained controllably by changing the parameters. We further prepare the stripe sample into grating and obtain regular diffraction patterns.